Hospitals show wide variations in patient outcomes of mortality and morbidity even when individual patient differences of acuity are controlled. While investigators have examined the relationship between nursing care variables and patient outcomes, identifying the contributions that nurses make to positive patient outcomes has eluded us. Expertise in nursing practice is one variable that may help explain some of the variation in patient outcomes. The early recognition of patient problems is an ability that has been closely associated with nursing expertise and theoretically a key variable in determining optimal outcomes. Currently, there are no suitable instruments available to measure the degree of nursing expertise among experienced nurses. The specific aims of this study are (a) to develop a theoretically based instrument that measures nurses' manifestation of early recognition of patient problems (Phase 1), and (b) to assess the feasibility of linking the measure of early recognition of patient problems with patient outcomes at both the individual and group level of analysis (Phase 2). Nurse and patient participants will be recruited from medical-surgical units and intensive care units of five large tertiary -care centers in the southeastern United States. Factor analysis will be conducted to determine the internal structure and cross structure of the items in the instrument. An exploratory correlational design will be used to examine athe relationship between group level early recognition and patient outcomes such as (a) severity-adjusted mortality, (b) function status, (c) length of stay, (d) unplanned physician or emergency room visits, (e) patient satisfaction with care, and (f) nosocomial infections. Because expertise is presumed to make a difference in patient outcomes, there is a need to the develop an instrument that can capture this dimension of nursing care. If the staff mix of expertise can be linked to outcomes, then we will be one step closer to designing units that provide cost-effective quality care with optimal patient outcomes.